1. Field
Example Embodiments relate to an infrared detector, and more particularly, to an infrared detector that is capable of detecting a wide bandwidth infrared spectrum.
2. Description of the Related Art
According to a principle of black body radiation, an object radiates a broadband electromagnetic wave that peaks at a specific wavelength according to a temperature. For example, an object radiates an infrared ray having a peak in a wavelength band at about 10 μm at room temperature. Bolometers are tools that absorb electromagnetic waves having an infrared (or terahertz) wavelength band radiated according to the black body radiation principle. The bolometer is configured to convert the absorbed electromagnetic waves into heat and then detect a temperature change due to the heat to measure radiation energy therearound.
Recently, in the development of micro electro mechanical system (MEMS) technologies, thermal imaging cameras in which a plurality of microbolometers are arranged in a two-dimensional array to acquire thermo images are being designed. To realize a high-resolution thermal camera having high temperature accuracy, a small-size pixel may be required. However, in a case where Salisbury screen type bolometers are used, in which a ground plate and a heat absorber are disposed at an interval of about λ/4 (where, λ is a centroid wavelength of an infrared wavelength band to be detected), when the pixel decreases in size, an energy amount incident into the pixel may be reduced. This reduction in incident energy may result in decreased absorption of heat resulting in a decrease in a temperature variation and a signal-to-noise ratio.
Lately, the use of bolometers using localized surface plasmon resonance (LSPR) is being proposed instead of using Salisbury screen type bolometers. Surface plasmon refers to a type of electromagnetic wave generated due to charge density oscillation of electrons that occurs on a surface of a metal. Bolometers using a plasmonic absorber may overcome limitations with respect to low absorption and low signal-to-noise ratio due to the LSPR.
However, since the plasmonic absorber may have relatively narrow bandwidth, it is difficult to effectively absorb heat in an entirety of the infrared region from about 8 μm to about 14 μm which is typically used for acquiring thermo images. Thus, various methods for increasing the resonance bandwidth of the plasmonic absorber are being proposed. For example, materials constituting the absorber may be substituted, or a plurality of resonators having different sizes may be disposed within one unit pixel.